1. Field of the Invention
The present invention relates to composite structures and their methods of manufacture, more particularly to structures used in composite aircraft construction.
2. Description of Related Art
Apparatus for the manufacture of structures from layers of composite material are well known. However, for some applications the existing apparatus has certain drawbacks.
Automated Tape Layer (ATL) apparatus places single layers of uncured composite pre-impregnated material on flat or contoured surfaces, but the apparatus is extremely complex and very expensive. The tape dispensed is unidirectional, so when making long, narrow parts where an angled ply or cross ply is needed, the tape laying head must traverse the part once for each width of tape, which makes the process extremely slow.
Another method of manufacturing composite parts is by use of Automated Fiber Placement (AFP) equipment. This is similar in nature to the ATL process discussed above, except that the material used is a thin ribbon or yarn, often referred to as a tow, of pre-impregnated composite material.
U.S. Pat. No. 5,954,917, assigned to the assignee of the present invention, and herein incorporated by reference, comprises a first station having at least one dispensing module, a second station where tape layers that have been deposited on the tool are vacuum treated in order to remove air entrapped between layers of the tape, and a track system which enables movement of the tool between the first and second stations as well as a tool storage station. In the apparatus of this patent and similar apparatus there are two established methods of obtaining the peripheral shape of the part in the form desired. In one method, each layer of composite material is pre-cut to its final dimensions at another station and then is kitted on spools for the final lay-up step. In another method the lay-up is performed with over-sized material, all compaction is performed and the part is either trimmed to shape at that point or cured to it's final condition and then trimmed. When a number of layers of composite material are trimmed, the ultrasonic knives that are customarily used, must travel very slowly.
Another method of manufacturing multiple layer composite parts is hand lay-up of the layers. In this method, the layers are usually trimmed to the proper shape and kitted at one station and then manually aligned with one another to build the lay-up desired. Correct positioning is handled either through physical templates or through projected light templates, usually using a projected laser system. While this method works, it is relatively slow, subject to human error, and not well suited to the production rates found in the manufacture of commercial aircraft.
Thus there is a need for a more efficient means of manufacturing multiple layer composite parts.